Latency and Dropouts on a Wireless Bridge
A farm uses a point-to-point wireless bridge to connect 6 cameras at a barn to the farmhouse NVR. Link is rated 300 Mbps but real throughput is ~40 Mbps. Cameras are 4 MP at 20 fps, H.265, average 4 Mbps each. Operators see periodic freezes and 2–4 s latency on live view, worse in rain. Recording sometimes shows gaps. The customer blames the cameras.
1. Where is the problem most likely, and how do you isolate it?
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40 Mbps real throughput vs 6 × 4 Mbps = 24 Mbps average leaves little headroom for peaks, retransmissions, and rain fade - the link, not the cameras, is the prime suspect. Isolate by:
- Checking per-camera bitrate statistics vs the link's actual throughput and error/retry counters.
- Testing with cameras disconnected one at a time to see when freezes stop.
- Comparing recording gaps to link error events (rain correlation is a strong clue).
- Confirming live view uses a low-bandwidth substream; if the client pulls the full stream for 6-up view, that alone can overload the link.
Freezes + latency + rain correlation + recording gaps all point to insufficient/error-prone wireless capacity, not camera faults.
2. What changes reduce load and improve resilience?
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Reduce demand and protect the link:
- Use substreams for live viewing (e.g. 640×360) so operators don't pull full 4 MP streams.
- Lower frame rate or cap max bitrate on the recording stream to fit within sustained throughput with margin for rain fade.
- Prioritize recording traffic / enable QoS on the bridge.
- Improve the wireless link (alignment, channel, antenna gain) or add capacity if peaks still exceed headroom.
- Verify recording resumes cleanly after link drops and that the NVR buffers/handles reconnects.
Re-measure throughput and error counters in dry and wet conditions before closing out.